This invention relates to a fluid filtering device and more particularly to a strainer construction for use in a automatic transmission for filtering oil which is circulated in the transmission as pressure transmitting and lubricating media. The oil is usually provided in a reservoir or oil pan located beneath a control valve body of the automatic transmission. The oil is sucked into the valve body serving as the input supply to a hydraulic control system of the transmission. Filtration through an oil strainer is provided prior to the entrance of the oil into the valve body.
The oil strainer removes particles of foreign matter which otherwise cause seizure or sticking of valves in time in the hydraulic control system. In this regard, it is the general practice in the prior art to provide an oil strainer at the entrance of the suction passage to the valve body. Thus, the oil strainer has a small filtering area when compared with the volume of the oil pan and the rate of oil flow through the suction inlet passage to the valve body. Therefore, the strainer is susceptible to early clogging. Replacement of the strainer is not a simple task.
Clogging of the oil strainer creates an increase in resistance to oil flow from the oil pan to the valve body and makes it difficult to maintain a rated oil pressure and rated flow quantities in the hyraulic control system of the transmission. Failure or improper operation of the transmission may result.
What is needed is strainer means able to assure rated oil flows to the valve body over extended periods of time without servicing.